I've yet to experience any issues with my 18" Compomotives. I've driven on a variety of loose surfaces inc. some with a lot of small chippings/stones. What I haven't done yet is drive through a lot of deep mud, having only been through a couple of isolated muddy sections.

You could ask the guys at Prospeed, they sell and fit Compomotives. Or talk to Compomotive themselves:

I have RSS 20" wheels fitted with Pirelli Verde 255/55/20's. That was a heck of an improvement regards ride. If you're ever up to Essex, you're welcome to have a go.

FFRR 2017 4.4SDV8 Autobiography. Cost so much I must be mad!
D4 HSE 2012 Like a second wife, more expensive but goes better! I almost cried this time!
D3 HSE 2006 (Almost 8 years together, true love)
Land Cruiser VX 1994 11 years together, wife cried when I p/ex'd for my D3